<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      let qk = 200,
        ck = 300,
        ye = 100;
      let option = prompt(
        "请选择您的操作：\n1、取款\n2、存款\n3、查看余额\n4、退出"
      );
      switch (+option) {
        case 1:
          alert(`你取了${qk}元`);
          break;
        case 2:
          alert(`你存了${ck}元`);
          break;
        case 3:
          alert(`你的银行卡余额是${ye}元`);
          break;
        case 4:
          break;
      }
    </script>
  </body>
</html>
